Integrated Bioethanol and Bioelectricity production from Ghanaian Seaweed Biomass
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Date
2021-07-12
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Abstract
This study investigated the potential of integrating bioethanol and bioelectricity
production technologies as an efficient means of maximising seaweed biomass
utilization. It particularly sought to examine optimal conditions for the production of
bioethanol from selected seaweeds, the bioelectricity potential of seaweed residue
using microbial fuel cells and the sustainability of the integrated bioethanol and
bioelectricity technologies on seaweeds. The motivation for this work is the growing
concerns over the dire food securities issues that could occur from the continued use
of edible biomass such as maize, cassava and sugarcane in commercial bioethanol
production. The study was conducted through the screening of pretreatment methods,
optimisation of dilute acid and enzymatic hydrolysis, screening of yeasts strains and
screening of ethanol production pathways with seaweeds as substrates. It also included
the evaluation of power generation, internal resistances and substrate consumption
from microbial fuel cells fed with seaweed bioethanol residue and; an Energy Return
on Investment analysis of various seaweed bioenergy production scenarios. The study
established that the optimal ethanol yields for Ghanaian seaweeds, U. fasciata, H.
dentata and S. vulgare were 5.06, 2.44 and 3.69% dry matter, respectively. This was
obtained via the SHF pathway through enzymatic hydrolysis with an optimal cellulase
dosage of 8 filter paper unit/g dry biomass and fermentation with S. cerevisiae SI17,
C8T17 or PT17 yeast strains. The study also found residues from seaweed bioethanol
production to be efficient substrates for use in microbial fuel cells since, it yielded
power densities between 0.46 and 0.50 W/m3 which were comparable to sodium
acetate by up to 52.62%. The integrated approach to seaweed biomass utilization was
considered successful since waste generation was reduced to as low as 24.43% from a
potential 79% from seaweed bioethanol production alone. It further established that
the production of both bioethanol and bioelectricity from Ghanaian seaweeds would
be sustainable based on the Energy Return on Investment value of 4.2 obtained after a
Life Cycle Assessment of the bioenergy processes. The study further established that
the production of bioethanol alone from seaweeds would not be sustainable
commercially despite a net gain in energy from its Life Cycle Assessment.
Description
A thesis submitted to the Department of Agricultural and Biosystems Engineering, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfilment of the requirements for the award of the degree of Doctor of Philosophy in Bioengineering.
Keywords
Integration, Bioethanol and Bioelectricity Production, Ghanaian Seaweed Biomass